Drip irrigation tubes of this kind are known in various designs. With such drip irrigation tubes a direct irrigation of plants is achieved. For this purpose at least one metering element can be installed in the tube in the region of each plant, through which metering element the water can emerge dropwise via an outlet opening and can irrigate the respective plant accordingly. With such drip irrigation tubes a very efficient and economical irrigation of plants can be achieved.
During the irrigation process the water in the drip irrigation tubes is under a certain pressure. In these drip irrigation tubes the metering elements are installed at a particular spacing apart from one another. In each of these metering elements there takes place in the metering region a pressure reduction of the water; the water escapes dropwise out of the drip irrigation tubes through the outlet openings. These drip irrigation tubes can have a great length. In the crops to be irrigated these drip irrigation tubes follow the unevenness or inclinations of the ground. Owing to the length of the drip irrigation tubes or respectively the differences in altitude to be overcome, a differing water pressure can occur in these drip irrigation tubes during the irrigation process. With the metering elements known from the state of the art there is the drawback that the same amount of water does not escape in all the metering elements over time, so that the individual plants are not irrigated equally. At places of the drip irrigation tube where the water pressure is high, more water thus escapes than at places where the water pressure in the drip irrigation tube is smaller, for the mentioned reasons.
Drip irrigation tubes are known that are provided with metering elements in which the labyrinth channel forming the metering region can be changed depending on the water pressure. For this purpose, with increase of the water pressure in the drip irrigation tube, the discharge cross section of the labyrinth channel is reduced, whereby a greater metering of the escaping water can be achieved at increased pressure in the tube. A narrowing of the discharge cross section of the labyrinth channel entails however the risk that the thus restricted discharge cross section can be clogged by soil particles located in the water. A clogging of a metering element can however have the consequence that the plants to be irrigated by means of this metering element can die. It is also not possible in a simple way to flush out a soiling or clogging of the metering element and to overcome the corresponding malfunction.